The exopeptidase dipeptidyl peptidase IV (DP IV, CD26, EC 3.4.14.5) is involved in a number of physiological regulation processes. On the one hand, DP IV is a peptidase which can change the activity of a number of peptide hormones, neuropeptides and chemokines in a very specific manner (Mentlein, Reg. Pep. 85, pp. 9-24 (1999) while on the other hand the DP IV protein molecule exerts protein-protein interactions, so mediating the regulation of intracellular signaling cascades. A growing number of peptide substrates containing proline, alanine or serine in the penultimate position are identified as substrates of DP IV in vitro and in vivo. Bioactive peptides which are substrates for DP IV and members of such regulation cascades are, among others, NPY, GIP, GLP-1, glucagons, VIP and PACAP. Furthermore, many DP IV-inhibitors belonging to different structural classes are known.
It is known that DP IV-Inhibitors may be useful for the treatment of impaired glucose tolerance and diabetes mellitus (International Patent Application, Publication Number WO 99/61431, Pederson R A et al, Diabetes. 1998 August; 47(8):1253-8 and Pauly R P et al, Metabolism 1999 March; 48(3):385-9). In particular WO 99/61431 discloses DP IV-Inhibitors comprising an amino acid residue and a thiazolidine or pyrrolidine group, and salts thereof, especially L-threo-isoleucyl thiazolidine, L-allo-isoleucyl thiazolidine, L-threo-isoleucyl pyrrolidine, L-allo-isoleucyl thiazolidine, L-allo-isoleucyl pyrrolidine, and salts thereof.
Further examples of low molecular weight dipeptidyl peptidase IV inhibitors are agents such as tetrahydroisoquinolin-3-carboxamide derivatives, N-substituted 2-cyanopyroles and -pyrrolidines, N-(N′-substituted glycyl)-2-cyanopyrrolidines, N-(substituted glycyl)-thiazolidines, N-(substituted glycyl)-4-cyanothiazolidines, amino-acyl-borono-prolyl-inhibitors, cyclopropyl-fused pyrrolidines and heterocyclic compounds. Inhibitors of dipeptidyl peptidase IV are described in U.S. Pat. Nos. 6,380,398, 6,011,155; 6,107,317; 6,110,949; 6,124,305; 6,172,081; and WO 95/15309, WO 99/61431, WO 99/67278, WO 99/67279, DE 198 34 591, WO 97/40832, DE 196 16 486 C 2, WO 98/19998, WO 00/07617, WO 99/38501, WO 99/46272, WO 99/38501, WO 01/68603, WO 01/40180, WO 01/81337, WO 01/81304, WO 01/55105, WO 02/02560 and WO 02/14271, WO 02/04610, WO 02/051836, WO 02/068420, WO 02/076450; WO 02/083128, WO 02/38541, WO 03/000180, WO 03/000181, WO 03/000250, WO 03/002530, WO 03/002531, WO 03/002553, WO 03/002593, WO 03/004496, WO 03/004498, WO 03/024965, WO 03/024942, WO 03/035067, WO 03/037327, WO 03/035057, WO 03/045977, WO 03/055881, WO 03/68748, WO 03/68757, WO 03/057666, WO 03057144, WO 03/040174 and WO 03/033524, the teachings of which are herein incorporated by reference in their entirety, especially concerning these inhibitors, their definition, uses and their production.
Definitions
The term “active site” as used in the claims and in the description is generally known to a person skilled in the art and means the catalytical site or region of DP IV and/or DP IV-like enzymes, which is responsible for the cleavage or biodegradation of the natural substrates of these enzymes.
The term “secondary binding site” as used in the claims and in the description means a site or region of DP IV and/or DP IV-like enzymes, which is different from the active site, e.g. a) a receptor site or b) a substrate recognition site or c) a regulatory site or allosteric site. The secondary binding site can a) affect the receptor function of DP IV and/or DP IV-like enzymes or b) affect the catalytic activity of DP IV and/or DP IV-like enzymes, especially the selectivity and/or specificity of these enzymes toward their substrates. Some secondary binding sites are complementary to the structure of the substrate of the enzymes, co-enzymes, co-factors and other compounds, which are involved in the activity and function of the enzyme. The enzymes may even have one or more secondary binding sites.
The secondary binding site is an element of the enzyme distinct from the catalytic site with a different form of regulation than the competition between substrates and inhibitors at the catalytic site (Darnell, J., Lodish, H. and Baltimore, D. 1990, Molecular Cell Biology 2nd Edition, Scientific American Books, New York, page 63).
The term “DP IV and/or DP IV-like enzymes” means DP IV or DP IV-like enzymes or both.
The term “activity modifying” as used in the claims and in the description means both the modification of the enzymatic activity as well as the modification of the selectivity or specificity of DP IV and/or DP IV-like enzymes. Especially preferred is the modification of the selectivity or specificity of DP IV and/or DP IV-like enzymes toward their natural substrates.
“Effectors”, as that term is used herein, are defined as molecules or ligands that interact with a secondary binding site of DP IV and/or DP IV-like enzymes, thereby changing their catalytical behaviour in vitro and/or in vivo. Effectors can increase or decrease the catalytical activity of the enzymes. Examples of effectors are activators or inhibitors. The effectors as used herein do not act at the active sites of enzymes, but at least one secondary binding site, e.g. a regulatory site, or an allosteric site. The term “effectors” is used herein synonymously with “agent” or “compound”.
The term “DP IV-inhibitor” is generally known to a person skilled in the art and means enzyme inhibitors, which interact with the active site or catalytical site of DP IV or DP IV-like enzymes or DP IV and/or DP IV-like enzymes and inhibit the catalytical activity of these enzymes.
The “use of effectors” encompasses one single effector or two or more effectors together. Preferred is the use of two effectors. Especially preferred is the use of one single effector.
“Conditions associated with diabetes mellitus” itself include hyperglycaemia, insulin resistance, including acquired insulin resistance and obesity. Further conditions associated with diabetes mellitus itself include hypertension and cardiovascular disease, especially atherosclerosis and conditions associated with insulin resistance. Conditions associated with insulin resistance include polycystic ovarian syndrome and steroid induced insulin resistance and gestational diabetes.
“Complications associated with diabetes mellitus” includes renal disease, especially renal disease associated with Type 2 diabetes, neuropathy and retinopathy.
Renal diseases associated with Type 2 diabetes include nephropathy, glomerulonephritis, glomerular sclerosis, nephrotic syndrome, hypertensive nephrosclerosis and end stage renal disease.
Diabetes mellitus is preferably Type 2 diabetes.
Classification of Diabetes
Clinical diabetes may be divided into four general subclasses, including (1) type 1 (caused by beta cell destruction and characterized by absolute insulin deficiency) (2) type 2 (characterized by insulin resistance and relative insulin deficiency (3) other specific types of diabetes (associated with various identifiable clinical conditions or syndromes) and (4) gestational diabetes mellitus. In addition to these clinical categories, two conditions—impaired glucose tolerance and impaired fasting glucose—refer to a metabolic state intermediate between normal glucose homeostasis and overt diabetes. These conditions significantly increase the later risk of diabetes mellitus and may in some instances be part of its natural history. It should be noted that patients with any form of diabetes might require insulin treatment at some point. For this reason the previously used terms insulin-dependent diabetes (for type 1 diabetes mellitus) and non-insulin-dependent diabetes (for type 2) have been eliminated.
Diabetes is currently classified as follows:
Clinical Diabetes
                1. Type 1 diabetes, formerly called insulin-dependent diabetes mellitus (IDDM) or “juvenile-onset diabetes”        2. Type 2 diabetes, formerly called non-insulin-dependent diabetes (NIDDM) or “adult-onset diabetes”        3. Other specific types                    a) Genetic defects of β-cell function (e.g., maturity-onset diabetes of the young [MODY] types 1-3 and point mutations in mitochondrial DNA)            b) Genetic defects in insulin action            c) Disease of the exocrine pancreas (e.g., pancreatitis, trauma, pancreatectomy, neoplasia, cystic fibrosis, hemochromatosis, fibrocalculous pancreatopathy).            d) Endocrinopathies (e.g. acromegaly, Cusing's syndrome, hyperthyroidism, pheochromocytoma, glucagonoma, somatostinoma, aldosteronoma)            e) Drug or chemical induced (e.g., glucocorticosteroids, thiazides, diazoxide, pentamidine, vacor, thyroid hormone, phenytoin [Dilantin], β-agonists, oral contraceptives)            f) Infections (e.g., congenital rubella, cytomegalovirus)            g) Uncommon forms of immune-mediated diabetes (e.g., “stiff-man”, syndrome, anti-insulin receptor antibodies)            h) Other genetic syndromes (e.g., Down, Klinefelter's, Turner's syndrome, Huntington's disease, myotonic dystrophy, lipodystrophy, ataxia-telangiectasia)                        4. Gestational diabetes mellitusRisk Categories        1. Impaired fasting glucose        2. Impaired glucose toleranceType 1 Diabetes Mellitus        
Patients with this disorder have little or no insulin secretory capacity and depend on exogenous insulin to prevent metabolic decompensation (e.g., ketoacidosis) and death.
Commonly but not always, diabetes appears abruptly (i.e., over days and weeks) in previously healthy non-obese children or young adults; in older age groups it may have a more gradual onset. At the time of initial evaluation the typical patient often appears ill, has marked symptoms (e.g., polyuria, polydipsia, polyhagia, and weight loss), and may demonstrate ketoacidosis. Type 1 diabetes is believed to have a long a symptomatic preclinical stage often lasting years, during which pancreatic beta cells are gradually destroyed by an autoimmune attack that is influenced by HLA and other genetic factors, as well as the environment. Initially, insulin therapy is essential to restore metabolism toward normal. However, a so-called honeymoon period may follow and last weeks or moths, during which time smaller doses of insulin are required because of partial recovery of beta cell function and reversal of insulin resistance caused by acute illness. Thereafter, insulin secretory capacity is gradually lost (over several years). The association of type 1 diabetes with specific immune response (HLA) genes and the presence of antibodies to islet cells and their constituents provides strong support for the theory that type 1 diabetes is an autoimmune disease. This syndrome accounts for lees than 10% of diabetes in United States.
Type 2 Diabetes Mellitus
Type 2, by far the most common form of the disease, is found in over 90% of the diabetic patient population. These patients retain a significant level of endogenous insulin secretory capacity. However, insulin levels are low relative to the magnitude of insulin resistance and ambient glucose levels. Type 2 patients are not dependent on insulin for immediate survival and ketosis rarely develops, except under conditions of great physical stress. Nevertheless, these patients may require insulin therapy to control hyperglycemia. Type 2 diabetes typically appears after the age of 40 years, has a high rate of genetic penetrance unrelated to HLA genes, and is associated with obesity. The clinical features of type 2 diabetes may be mild (fatigue, weakness, dizziness, blurred vision, or other non-specific complaints may dominate the picture) or may be tolerated for many years before the patient seeks medical attention. Moreover, if the level of hyperglycemia is insufficient to produce symptoms, the disease may become evident only after complications develop.
Other Specific Types of Diabetes
This category encompasses a variety of diabetic syndromes attributed to a specific disease, drug, or condition. Genetic research has provided new insights into pathogenesis of MODY, which was formerly included as a form of type 2 diabetes. MODY encompasses several genetic defects of beta cell function, among which mutations at several genetic loci on different chromosomes have been identified. The most common forms—MODY type 3—is associated with a mutation for a transcription factor encoded on chromosome 12 named hepatocyte nuclear 1α (HNF 1, also known as TCF1) and -MODY type 2 is associated with mutations of the glucokinase gene (on chromosome 7) Mutations of the HNF-4α gene (on chromosome 20) are responsible for type 1 of MODY. Each of these conditions is inherited in an autosomal dominant pattern. Two new rare forms of MODY are associated with mutations of the HNF-1β (on chromosome 17) and an insulin gene transcription factor termed PDX-1 or 1DX-1 (on chromosome 13).
The distinction between the various subclasses of diabetes mellitus is usually made on clinical grounds. However, a small subgroup of patients are difficult to classify, that is, they display features common to both type 1 and 2 diabetes. Such patients are commonly non-obese and have reduced insulin secretory capacity that is not sufficient to make them ketosis prone. Many initially respond to oral agents but, with time, require insulin. Some appear to have a slowly evolving form of type 1 diabetes, whereas others defy easy categorization.
Gestational Diabetes
The term gestational diabetes describes women with impaired glucose tolerance that appears or is first detected during pregnancy. Gestational diabetes usually appears in the 2nd or 3rd trimester, a time when pregnancy-associated insulin antagonistic hormones peak. After delivery, glucose tolerance generally (but not always) reverts to normal.
Diagnosis
The diagnosis of diabetes is usually straightforward when the classic symptoms of polyuria, polydipsia, and weight loss are present. All that is required is a random plasma glucose measurement from venous blood that is 200 mg/dL or greater. If diabetes is suspected but not confirmed by a random glucose determination, the screening test of choice is overnight fasting plasma glucose level. The diagnosis is established if fasting is equal to or greater than 126 mg/dL on at least two separate occasions.
Related Conditions
Impaired Glucose Tolerance and Impaired Fasting Glucose
Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are terms applied to individuals who have glucose levels that are higher than normal, (under fed or fasting conditions, respectively) but lower than those accepted as diagnostic for diabetes mellitus. Both conditions are associated with an increased risk for cardiovascular disease, but do not produce the classic symptoms or the microvascular and neuropathic complications associated with diabetes mellitus. In a subgroup of patients (about 25 to 30%), however, type 2 diabetes eventually develops.
Impaired Glucose Metabolism
Impaired Glucose Metabolism (IGM) is defined by blood glucose levels that are above the normal range but are high enough to meet the diagnostic criteria for type 2 diabetes mellitus. The incidence of IGM varies from country to country, but usually occurs 2-3 time more frequently than overt diabetes. Until recently, individuals with IGM were felt to be pre-diabetics, but data from several epidemiological studies argue that subjects with IGM are heterogeneous with respect to their risk of diabetes and their risk of cardiovascular morbidity and mortality. The data suggest that subjects with IGM, in particular, those with impaired glucose tolerance (IGT), do not always develop diabetes, but whether they are diabetic or not, they are, nonetheless, at high risk for cardiovascular morbidity and mortality. Among subjects with I GM, about 58% have Impaired Glucose tolerance (IGT), another 29% have impaired fasting glucose (IFG), and 13% have both abnormalities (IFG/IGT). As discussed above, IGT is characterized by elevated post-prandial (post-meal) hyperglycemia while IFG has been defined by the ADA (American Diabetes Association) on the basis of fasting glycemic values.
The categories of (a) normal glucose tolerance (NGT), (b) impaired glucose metabolism (IGM) and (c) overt type 2 diabetes mellitus are periodically revised and adopted by the Expert Committee of the American Diabetes Association (ADA). The actual values as defined in “Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care (26) 1, 2003, 5-20” and “The Diabetes Ready-Reference Guide for Health Care Professionals, 2000, published by the American Diabetes Association” are:                a) Normal Glucose Tolerance (NGT)=fasting glucose level <6.1 mmol/L or less than 110 mg/dl and a 2h post-prandial glucose level of <7.8 mmol/L or <140 mg/dl.        b) Impaired Glucose Metabolism (IGM) is impaired fasting glucose (IFG) defined as IFG=fasting glucose level of 6.1-7.0 mmol/L or 110-126 mg/dl and/or impaired glucose tolerance (IGT)=a 2 h post-prandial glucose level (75 g OGTT) of 7.8-11.1 mmol/L or 140-200 mg/dl).        c) Type 2 diabetes=fasting glucose of greater than 7 mmol/L or 126 mg/dl or a 2 h post-prandial glucose level (75 g OGTT) of greater than 11.1 mmol/L or 200 mg/dl.        
These criteria were defined using the WHO recommended conditions for administration of an oral glucose tolerance test (75 g O GTT) i. e., the oral administration of a glucose load containing the equivalent of 75 g of anhydrous glucose dissolved in water with a blood sample taken 2 hours later to analyze to post-prandial glucose. Other OGTT test conditions have confirmed the associated risks of the IGT and IFG categories including: 1) using 50 g glucose instead of 75 g, 2) using a casual (non-fasting) glucose sample as the analyte, and 3) analysing the post-prandial glucose at 1 hour rather than 2 hours post-glucose load. Under all of these conditions, the glycemic categories defined above have been linked to the increased risks described below, but the standardized OGTT is preferred in order to minimize variations in test results.
Insulin resistance is not primarily due to a diminished number of insulin receptors but to a post-insulin receptor binding defect that is not yet understood. This resistance to insulin responsiveness results in insufficient insulin activation of glucose uptake, oxidation and storage in muscle and inadequate insulin repression of lipolysis in adipose tissue and of glucose production and secretion in the liver.
The term “subject” as used herein, refers to an animal, preferably a mammal, most preferably a human, who has been the object of treatment, observation or experiment.
The term “therapeutically effective amount” as used herein, means that amount of active compound or pharmaceutical agent that elicits the biological or medicinal response in a tissue system, animal or human, being sought by a researcher, veterinarian, medical doctor or other clinician, which includes alleviation of the symptoms of the disease or disorder being treated.
As used herein, the term “pharmaceutically acceptable” embraces both human and veterinary use: for example the term “pharmaceutically acceptable” embraces a veterinarily acceptable compound or a compound acceptable in human medicine a health care.
Throughout the description and the claims the expression “acyl” can denote a C1-20 acyl residue, preferably a C1-8 acyl residue and especially preferred a C1-4 acyl residue; “cycloalkyl” can denote a C3-12 cycloalkyl residue, preferably a C4, C5 or C6 cycloalkyl residue; and “carbocyclic” can denote a C3-12 carbocyclic residue, preferably a C4, C5 or C6 carbocyclic residue. “Heteroaryl” is defined as an aryl residue, wherein 1 to 4, and more preferably 1, 2 or 3 ring atoms are replaced by heteroatoms like N, S or O. “Heterocyclic” is defined as a cycloalkyl residue, wherein 1, 2 or 3 ring atoms are replaced by heteroatoms like N, S or O. “Peptides” are selected from dipeptides to decapeptides, preferred are dipeptides, tripeptides, tetrapeptides and pentapeptides. The amino acids for the formation of the “peptides” can be selected from those listed above.
Throughout the description and the claims the expression “alkyl” can denote a C1-50 alkyl group, preferably a C6-30 alkyl group, especially a C8-12 alkyl group; for example, an alkyl group may be a methyl, ethyl, propyl, isopropyl or butyl group. The expression “alk”, for example in the expression “alkoxy”, and the expression “alkan”, for example in the expression “alkanoyl”, are defined as for “alkyl”; aromatic compounds are preferably substituted or optionally unsubstituted phenyl, benzyl, naphthyl, biphenyl or anthracene groups, which preferably have at least 8 C atoms; the expression “alkenyl” can denote a C2-10 alkenyl group, preferably a C2-6 alkenyl group, which has the double bond(s) at any desired location and may be substituted or unsubstituted; the expression “alkynyl” can denote a C2-10 alkynyl group, preferably a C2-6 alkynyl group, which has the triple bond(s) at any desired location and may be substituted or unsubstituted; the expression “substituted” or substituent can denote any desired substitution by one or more, preferably one or two, alkyl, alkenyl, alkynyl, mono- or multi-valent acyl, alkanoyl, alkoxyalkanoyl or alkoxyalkyl groups; the afore-mentioned substituents may in turn have one or more (but preferably zero) alkyl, alkenyl, alkynyl, mono- or multi-valent acyl, alkanoyl, alkoxyalkanoyl or alkoxyalkyl groups as side groups; organic amines, amides, alcohols or acids, each having from 8 to 50 C atoms, preferably from 10 to 20 C atoms, can have the formulae (alkyl)2N— or alkyl-NH—, —CO—N(alkyl)2 or —CO—NH(alkyl), -alkyl-OH or -alkyl-COOH.